In recent times much effort has been devoted to developing new and useful osmotic powered devices for delivering useful agents to a predetermined environment of use. For example, U.S. Pat. No. 3,760,984 issued to Theeuwes discloses a device comprising an inner collapsible container carrying on its outer surface a layer of an osmotic solute and a distinct layer of a polymer permeable to fluid and impermeable to the solute. The device has an inventive means for filling the container. In U.S. Pat. No. 3,971,376 issued to Wichterle, a device is disclosed comprising a capsule having a unitary wall formed of a substantially non-collapsible elastic material that is exposed to the environment of use. A textile fabric is embedded in the elastic material to impart strength and minimize problems due to the inherent mechanical properties of the material that occur during uptake of fluid. In U.S. Pat. No. 3,995,631 issued to Higuchi, et al., there is disclosed a bag formed of a flexible material encapsulated with a film of an osmotically effective solute surrounded by a wall having in at least a part controlled permeability to an exterior fluid. The above described osmotic devices are useful for delivering many agents, and they represent a valuable contribution to the agent delivery art. The present invention is an advancement in the osmotic delivery art by making available a new pressure generating means that can supply the self-contained power needed for propelling an agent from an osmotic device.